A coating apparatus that includes a rotary drum is used for providing a film coating, a sugar coating or the like to each of tablets, soft capsules, pellets, granules and other similar materials (hereinafter, collectively referred to the particles) of pharmaceutical drugs, food, agricultural chemicals and the like.
The coating apparatus of this type is disclosed in, e.g., Patent Documents 1 and 2.
Patent Document 1 discloses a coating apparatus that includes a ventilatory rotary drum being driven to rotate about a horizontal axis. The rotary drum is structured with a polygonal sleeve-like circumferential wall portion, a polygonal pyramid-shaped one end portion that extends from one end of the circumferential wall portion toward one side in the axial direction, and a polygonal pyramid-shaped other end portion that extends from other end of the circumferential wall portion toward the other side in the axial direction. To each face of the circumferential wall portion, a porous plate is attached. The porous portion of each porous plate provides ventilation to the circumferential wall portion. Then, a jacket is attached on the outer circumferential side of each porous plate, whereby a ventilation channel is formed between the jacket and each porous plate.
Further, on the other end side of the rotary drum, that is, on the side where a rotary drive mechanism including a motor or the like is installed, a ventilation mechanism that controls ventilation of treatment gas such as dry air to the rotary drum is installed. This ventilation mechanism has a function of establishing communication between ventilation channels that arrive at prescribed positions in accordance with the rotation of the rotary drum and an air supply duct and an air discharge duct, respectively.
For example, when a certain ventilation channel arrives at the top portion of the rotary drum in accordance with the rotation of the rotary drum, that ventilation channel communicates with the air supply duct; and when a certain ventilation channel arrives at the bottom portion of the rotary drum, that ventilation channel communicates with the air discharge duct. Accordingly, the treatment gas introduced from the air supply duct to the ventilation channel at the top portion of the rotary drum flows into the rotary drum via the porous plate at the top portion of the circumferential wall portion. After passing through the inside of a particle layer (tumbling bed), the treatment gas flows out to the ventilation channel via the porous plate at the bottom portion of the circumferential wall portion, and further passes through the ventilation channel to be discharged to the air discharge duct.
Patent Document 2 discloses a structure which is a coating apparatus including a ventilatory rotary drum that accommodates therein particles to be processed and that is driven to rotate about its axis. The rotary drum has, along its axial direction, a one end portion, an other end portion, and a circumferential wall portion that allows the one end portion and the other end portion to be continuous. The other end portion is positioned on the side of a rotary drive mechanism that drives the rotary drum to rotate. A ventilation port is provided to each of the one end portion and the other end portion. The ventilation port provided to one of the one end portion and the other end portion serves as an air supply port for supplying the treatment gas from the outside to the inside of the rotary drum. The ventilation port provided to the other one of the one end portion and the other end portion serves as an air discharge port for discharging the treatment gas from the inside of the rotary drum to the outside. The treatment gas supplied into the rotary drum via the air supply port passes through the inside of a particle layer in the rotary drum, and is discharged from the air discharge port.
Though the rotary drum is of ventilatory, the ventilation port is provided to each of the one end portion and the other end portion, and the circumferential wall portion is not provided with any ventilation portions (porous portions) for supplying or discharging air. Accordingly, it is not necessary to provide a complicated ventilation structure in which the ventilation portions (porous portions) of the circumferential wall portion are covered with jackets from the outer circumferential side to form ventilation channels as seen in the conventional ventilatory rotary drum. That is, while the coating apparatus of this invention includes a ventilatory rotary drum, the circumferential wall portion of the rotary drum has no ventilation portions (porous portions) for supplying or discharging air. In other words, the circumferential wall portion of the rotary drum has an air-tight structure. Further, there are no ventilation channels covered by jackets on the outer circumferential side of the circumferential wall portion of the rotary drum. Accordingly, as compared to the conventional apparatus, the cleaning work and the validation work after cleaning can easily and surely be performed.
The ventilation port of one of the one end portion and the other end portion is dedicated to supplying air, and the other ventilation port is dedicated to discharging air. The treatment gas (hot air, cold air or the like) supplied into the rotary drum via the air supply port of the one end portion or that of the other end portion passes through the particle layer in the rotary drum and is discharged from the air discharge port of the other end portion or that of the one end portion. Thus, ventilation is carried out throughout the inside of the particle layer, and treatment such as drying of the particle layer can evenly and fully be performed.
The rotary, drum is installed in a state in which its axis forms a prescribed angle θ that falls within a range of 0°≦θ≦90° relative to the horizontal line. That is, the rotary drum is installed and operated in one of the states in which: its axis is in parallel with the horizontal line (θ=0°); its axis is in parallel with the vertical line (θ=90°); and its axis is tilted relative to the horizontal line (0°<θ<90°). Preferably, the rotary drum is installed in a state in which its axis is tilted by a prescribed angle θ relative to the horizontal line. In this case, the tilt angle θ of the axis is set to 20°≦θ≦70°, more preferably 30°≦θ≦45°, and particularly θ=30° or θ=45°.
Since the axis of the rotary drum is tilted by the prescribed angle θ relative to the horizontal line, the bulk volume of the particles that can be treated in the rotary drum increases. Therefore, the throughput per treatment increases, whereby the production efficiency improves. Further, as the rotary drum rotates about the tilted axis, the particles accommodated in the rotary drum flow in accordance with the rotation of the rotary drum in a state associated with the movement in the rotary direction and the movement in the axial direction. Therefore, the effect of agitating and mixing the particle layer is great. For example, even in a case where a so-called baffle (agitator blade) is not arranged inside the rotary drum, sufficient agitating and mixing effect can be obtained. It goes without saying that, when the baffle is used in combination, a greater agitating and mixing effect can be obtained. When the axis of the rotary drum is tilted, normally, the rear end portion of the rotary drum is positioned on the tilted downward side.